Jakarta. A strong La Nina weather effect threatens more drenching of waterlogged coal production areas in Australia and Indonesia over the next six months, cutting exports and driving up prices just as Chinese winter demand kicks in.

As a result, prices for Australia’s thermal coal, the Asian benchmark, could move as high as $120 per ton before the end of the year, from around $109 now, said Mark Pervan, head of commodity research at ANZ Bank in Sydney. A price above $120 would be the highest since September 2008.

“The likelihood of a strong winter coming through in north Asia, dovetailed with what looks like a pretty tight supply backdrop, will probably see the market move up another $10 a ton,” he said.

Australia is the world’s largest coal exporter and, combined with Indonesia, produces more than 10 percent of the world’s thermal coal supplies.

The La Nina effect has raised forecasts for rainfall in both top coal exporters, upping the number of cyclones expected in Australia’s northeastern coal belt to six or seven from an average four.

“We’re heading into the time of year between now and April next year where cyclone season hits up north,” said Gavin Wendt, a senior resource analyst at Mine Life in Sydney.

“We always get a seasonal spike in thermal coal pricing around about this time of the year, but that’s going to be exacerbated by strong Chinese demand, and don’t forget Indian buying as well.”

Chinese demand has escalated recently as the world’s largest coal consumer tries to stockpile ahead of a frosty winter, with buyers hunting for coal deals in Asia and also casting their nets further afield, most recently striking a deal for South African coal.

Although Chinese stockpiles are relatively high at more than six million tons, spot supplies in China have tightened over the past month as cold weather disrupted some coal production.

Indian import demand for coal is expected to grow by more than 80 percent by 2012, and India, already one of Indonesia’s main customers, is expected to feed its coal appetite from Indonesia.

Unseasonably wet weather has already hit Indonesian production, particularly from smaller miners, and with months of rain still ahead, exports are likely to be affected into 2011.

“The majority of Indonesian coal producers have already seen their output falling about 5 to 10 percent below where they usually are … this time of year,” said Andreas Bokkenheuser, an analyst with UBS in Singapore.

Smaller miners have been particularly hard hit as they fall months behind their output targets, wiping out tonnage they need to ship for existing contracts.

“We have to reject requests from buyers even for next year delivery because we don’t have any coal,” said one East Kalimantan producer with an output of about 200,000 tons a month.

Some of Australia’s thermal coal production has already been affected by unseasonal rains in Queensland state, which produces mostly coking coal.

Predictions that northeastern Australia will get soaked this season point to a high probability that the world’s largest coal port, Newcastle, will suffer backlogs this season, analysts said.

Wet weather has resulted in export disruptions from Newcastle as both production and transport to the port are derailed. Some in the industry have warned that this cyclone season may resemble the 2007-08 season, when strong demand before the global financial crisis combined with wet weather to cause prices of both coking and thermal coal to spike.

“Time will tell how much damage La Nina can make, but at the current stage, it’s not looking good at all. It will be 2007 all over again,” one Sydney-based trader said.